fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL

{
  "id": "30df6a40c3741ac95a570bfed1b8c50cc8eac772eb17eca15a207e2f89de0638",
  "url": "https://osv.dev/vulnerability/CVE-2022-50778",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL With CONFIG_FORTIFY=y and CONFIG_UBSAN_LOCAL_BOUNDS=y enabled, we observe a runtime panic while running Android's Compatibility Test Suite's (CTS) android.hardware.input.cts.tests. This is stemming from a strlen() call in hidinput_allocate(). __compiletime_strlen() is implemented in terms of __builtin_object_size(), then does an array access to check for NUL-termination. A quirk of __builtin_object_size() is that for strings whose values are runtime dependent, __builtin_object_size(str, 1 or 0) returns the maximum size of possible values when those sizes are determinable at compile time. Example: static const char *v = \"FOO BAR\"; static const char *y = \"FOO BA\"; unsigned long x (int z) { // Returns 8, which is: // max(__builtin_object_size(v, 1), __builtin_object_size(y, 1)) return __builtin_object_size(z ? v : y, 1); } So when FORTIFY_SOURCE is enabled, the current implementation of __compiletime_strlen() will try to access beyond the end of y at runtime using the size of v. Mixed with UBSAN_LOCAL_BOUNDS we get a fault. hidinput_allocate() has a local C string whose value is control flow dependent on a switch statement, so __builtin_object_size(str, 1) evaluates to the maximum string length, making all other cases fault on the last character check. hidinput_allocate() could be cleaned up to avoid runtime calls to strlen() since the local variable c",
    "evidence": "osv:CVE-2022-50778",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.19.17",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.0.3",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2022-50778",
      "aliases": [
        "CVE-2022-50778"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "3009f891bb9f328945ebd5b71e12df7e2467f3dd"
                },
                {
                  "fixed": "ed42391164e6839a48aaf4c53eefda516835e799"
                },
                {
                  "fixed": "5d59ad2bfb35fccfe2ad5e8bb8801f6224d3f7d4"
                },
                {
                  "fixed": "d07c0acb4f41cc42a0d97530946965b3e4fa68c1"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2022-50778.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "5.19.17"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.20.0"
                },
                {
                  "fixed": "6.0.3"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2022-50778.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:31.500110841Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/5d59ad2bfb35fccfe2ad5e8bb8801f6224d3f7d4",
        "https://git.kernel.org/stable/c/d07c0acb4f41cc42a0d97530946965b3e4fa68c1",
        "https://git.kernel.org/stable/c/ed42391164e6839a48aaf4c53eefda516835e799",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/50xxx/CVE-2022-50778.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2022-50778",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/50xxx/CVE-2022-50778.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2022-50778",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 498668,
  "published_at": "2025-12-24T13:06:07.182+00:00"
}